Eli, I think we can solve the three situations described with following 
algorithm/idea/inspiration [1]: through a configurable variable 
(yank-media-image-types ?). That would allow you to be able to select 
among all options (that for certain cases could be interesting, say 
"expert mode", I know what I am doing, verbose mode, etc.), and also, a 
way to filter out certain candidates based on what you need.

Making that variable equal to nil would be as it is now, and configuring 
it to "image/png", would only select one. I think others were thinking 
about a regex. As you wish, I only need some sort of filter, and I don't 
care too much on the detail of how it is configured.

[1]
#+begin_src emacs-lisp

(defun my/filter (lst allowed)
   "Filter elements from LST based on ALLOWED. If no match is found, 
return LST."
   (if (null allowed)
       lst
     (let ((filtered
            (delq nil (mapcar
                       (lambda (x)
                         (when
                             (member x allowed) x)) lst))))
       (if (null filtered) lst filtered))))

(defun my/select (lst allowed)
   (if (equal (length allowed) 1)
       allowed
     (completing-read
      "Several types available, choose one:"
      (my/filter lst allowed))))

(setq my/candidates '("image/png"
                       "image/pbm"
                       "image/xbm"
                       "image/xpm"
                       "image/jpeg"
                       "image/tiff"
                       "image/webp"))

;; 1. I only want png
(my/select my/candidates '("image/png"))
;; 2. I only want to select between png and/or jpeg
(my/select my/candidates '("image/png" "image/jpeg"))
;; 3. expert mode (just like it is now)
(my/select my/candidates nil)

;; example of how you would customize the variable
(setq yank-media-image-types '("image/png"))
#+end_src

On 2024-09-23 15:35, Eli Zaretskii wrote:
>> Date: Mon, 23 Sep 2024 15:00:54 -0300
>> Cc: visuweshm@gmail.com, emacs-devel@gnu.org
>> From: pinmacs <pinmacs@cas.cat>
>>
>> Before yank-media, I was using org-download [1], so I got used to just
>> insert a screenshot with no question to answer (such as the type of the
>> image).
>>
>> Recently, I moved to yank-media, but to have the same functionality, I
>> had to tweak it a little bit, full detail here [2].
>>
>> I see utility on asking for the image/png and image/jpeg and here you
>> have details why you would care about [3].
> This just says that PNG is always preferable to JPEG if both are
> available.  As I already said, I'm okay with the idea of having C-y or
> similar key to decide which format to use, and so what you are saying
> (and I agree) that it should always choose PNG if Emacs supports it.
>
> What I still do not understand is what would be the reason for the
> user to prefer JPEG over PNG.  More generally, if Emacs can support N
> formats out of those available in the clipboard, why would the user
> want to be shown only 1 < M < N out of them?
>
> Furthermore, your request was even more broad and general: it asked
> for some filtering infrastructure, and I'm still trying to understand
> why that would be needed.  The discussion to which you point on the
> Org list doesn't explain the rationale, either.
>
> Bottom line: I'm okay with offering two yank-media alternatives:
>
> (1) via a command that selects a single most appropriate format based
> on some (yet to be defined) algorithm; and
> (2) via showing the list of all the formats that the running Emacs
> supports and asking the user to choose one.
>
> If we can agree on this, we should now discuss those algorithms for
> selecting a single media type.
>
> Thanks.
>